Package for heating a food product

ABSTRACT

An ovenable container for pizza or other heatable food products includes a vent in the upper portion of the container and a metal region on the lower portion of the container. The container gives more consistent heating of the food product with reduced edge dryness.

[0001] This invention relates to an ovenable enclosure forheating/cooking and particularly to a box for pizza, preferably a boxsuitable for frozen pizza.

[0002] Many different kinds of such heating enclosures are known, someof which comprise the original packaging in which a frozen food productis sold. In the latter case, the kind of packaging will depend on theheating/cooking medium to be used. For example different kinds ofpackaging are often required for oven heated and microwave heatedproducts. The former must be adapted to resist considerable externalheat radiation yet allow the food product to be heated, whereas thelatter is heated indirectly by material within the packaging.

[0003] Food products intended to be heated by microwave may require someadditional radiated heat in order to give a fully cooked and ‘browned’appearance. For that reason heating enclosures are known which include ametallic coating adapted to give enhanced heating in selected areas ofthe enclosure. One such microwave enclosure is known from EP-A-0336325.A microwave oven may include a radiant element to ensure browning.

[0004] These types of heating enclosures have the advantage that thecontents need not be handled prior to serving the hot food product as ameal. The use of packaging as a cooking enclosure for microwaveablefrozen food has had an important effect on the quality and consistencyof the resulting hot food product. This is because the cooking timer ofa microwave oven tends to be very accurate and because the energy sourceceases at the end of the cooking time. Thus the cooking environment canbe closely controlled by the packaging to give an optimum result.

[0005] Oven heated food products are more problematic because there aremany variables which cannot be controlled, and because users have manymore options available. For example despite written instructions, a usermay not wait for an oven to reach a required temperature, the oven mayhave an uneven heat distribution, oven temperature control is oftenrather poor, and cooking time is difficult to control accuratelyparticularly because residual heat will continue to cook the producteven if the energy source is turned off.

[0006] A particular problem arises due to the large thermal mass of ovenheated frozen pizza where dryness of the pizza crust and/or burning ofthe topping can be difficult to avoid. What is required is a heatingenclosure capable of more closely controlling the cooking environment inan oven so as to reduce the variability in the quality of the hot foodproduct, and preferably an enclosure that is adapted to resist up to300° C. for up to one hour.

[0007] According to the present invention there is provided an enclosurefor pizza, the enclosure being of ovenable material and adapted forexposure to a source of heating energy, wherein the enclosure includes alower surface adapted to support a pizza and an upper surface adapted tocover the pizza, the upper surface having an openable vent in a midregion thereof whereby the interior of the enclosure can be ventedduring heating thereof. The pizza may be frozen or chilled, and may bepart cooked.

[0008] Such an enclosure permits the heating/cooking environment withinthe enclosure to be closely controlled, and to better ensure that theheated/cooked food product is to the required standard. Naturally, thematerial of the enclosure should be capable of exposure to heatingenergy without imparting any flavour or odour taint to pizza in theenclosure.

[0009] In one embodiment, the upper surface of the enclosure comprisesan inner layer having a pre-formed vent or vents therein, and an outerlayer which hermetically seals the enclosure for sale and transit, andwhich is removable just before heating/cooking. The outer layer may, forexample, be a film of any conventional and suitable kind.

[0010] The vent or vents may alternatively be part sheared through thepackaging or otherwise defined by lines of weakness whereby thehermetical seal is broken as the vent or vents are opened.

[0011] A typical pizza is approximately circular and contained in anenclosure which is square in plan and close fitting. In a preferredembodiment a single vent is centred on the pizza and is preferablycircular. The vent area is preferably in the range 5-80% of the uppersurface area of the enclosure, most preferably in the range 20-60%.

[0012] In another embodiment the vent area is in the range 10-70% of thearea of the pizza, most preferably in the range 20-60%. In the case of asingle circular vent the diameter ratio may be in the range 1:6 to 1:2and alternatively in the range 1:4 to 1:3. Such an arrangement gives afavourable heating/cooking environment.

[0013] A plurality of vents may be provided and comprise 40-80% of thesurface area of approximately the central 50% of the lid, and from 5-25%of the remainder.

[0014] A vent in the upper surface of the enclosure is also useful sinceit permits the user to see the pizza before cooking, and to inspect thepizza during cooking. This has been found to be an important advantagesince users tend to want to see the unheated food product andaccordingly will open the enclosure even if instructions require theenclosure to remain closed. Accordingly the invention also provides asolution to this inevitable urge, thus permitting the enclosure toperform the intended purpose of better controlling the heating/cookingenvironment.

[0015] The enclosure of the invention is preferably close fitting to thepizza, and in particular the inside of the upper surface is spaced fromthe pizza by a relatively small distance. Preferably the interior heightof the enclosure is not more than about 150% of the thickness of thepizza, and is most preferably in the range 100-150%. In a preferredembodiment the interior height of the enclosure is about equal to 120%of the thickness of the pizza.

[0016] One enclosure according to the invention comprises a closefitting square box for a round frozen pizza, typically of about 225 mmin diameter. The pizza sits on the base of the box and is spaced fromthe inside top surface by a distance of around 5-10 mm. The uppersurface of the box contains a central circular vent of about half thewidth of the pizza, and in the range 90-135 mm. In a preferredembodiment, a vent of 120 mm in diameter is provided.

[0017] A pizza cooked in an oven in such an enclosure avoids the dryedge characteristic of cooking on a simple plate-like base. Moistureloss is typically reduced from around 10% to 3%, the retained moisturemaintaining a soft pizza edge. The vent allows even browning of the topof the pizza and improves the overall texture of the pizza, whilstavoiding the characteristic pale appearance of a pizza cooked in aclosed environment.

[0018] Venting may be provided in the sides of a box-like enclosuretypically from 5-25% of the side surface area. Such venting may beprovided in any of the ways mentioned above.

[0019] The lower surface of the enclosure may define a tray for thepizza and have upstanding sides to confine the pizza therein. One ormore sides may be adapted to collapse in order to permit the cookedpizza to slide from the enclosure onto a plate.

[0020] The pizza preferably rests on a metal plate, typically acentrally placed circular metal disc having a surface area in the range5-80% of the area of the lower surface of the enclosure. The metal maybe of any suitable composition, for example aluminium, copper or steelhaving a suitable protective coating to avoid e.g. odour taint. Themetal plate may comprise a foil sheet of 50 micron thickness, or berelatively smaller in area and have a greater thickness.

[0021] The purpose of the metal plate is to provide a highly conductiveheat source adapted to promote heat transfer to the centre of the pizza,thereby to improve the taste, texture, smell and flavour of the hot foodproduct.

[0022] The preferred size and thickness of the metal plate is selectedempirically to suit the degree of additional heat transfer which isrequired, and will depend to some extent on the mass of the plate, andthe nature of the pizza topping.

[0023] In a preferred embodiment an aluminium foil disc of 50 micronthickness and in the diameter range 60-90 mm is provided for a pizza of225 mm in diameter. In conjunction with the vent or vents, the source ofdirect thermal energy gives a particularly effective and adaptableheating/cooking enclosure, in which cooking conditions can be optimisedto suit a pizza of known characteristics.

[0024] In a particularly preferred embodiment a foil disc of 75 mm iseffective in improving temperature distribution through the cookedpizza, giving a more even temperature, and a slightly reduced overalltemperature.

[0025] The metal plate is preferably substantially smaller than thepizza, and typically has a diameter in the range 25-40% of the diameterof the pizza. Such an arrangement avoids an over moist pizza basetypical of a foil tray for the pizza, and avoids excessive heat transferaway from the pizza after removal from the oven.

[0026] Such foil disc is preferably used in an enclosure having a ventarea greater than or equal to the area of the disc. In a preferredembodiment the diameter of the disc is about 75% of the diameter of acircular vent.

[0027] The enclosure may further include an embossed support surface forthe pizza. Such a surface permits better crisping of the pizza base byassisting moisture removal.

[0028] An aperture or apertures may be provided in the pizza supportsurface to further provide moisture removal in selected areas andcrisping of the base.

[0029] The upper surface preferably comprises a lid having dependingsides which may abut or overlap the lower surface. In the preferredembodiment the enclosure is rectangular, and the lid is hinged to thetray along one edge thereof.

[0030] Preferably the upstanding and/or depending sides are collapsibleso that the pizza can be easily portioned and removed for eating.

[0031] The enclosure may have an outer layer which both hermeticallyseals the contents thereof, and carries printed product information andthe like. In this way, printing of the enclosure itself is avoided, andthus the inner packaging can be optimised as a cooking enclosure withoutreference to external appearance and/or consumer perception.

[0032] Other features of the invention will be apparent from thefollowing description of preferred embodiments shown by way of exampleonly in the accompanying drawings in which:

[0033]FIG. 1 illustrates a first cooking enclosure according to theinvention, and

[0034]FIG. 2 illustrates a second cooking enclosure according to theinvention.

[0035] With reference to the FIG. 1, a square flip-top box 10 of a heatresistant taint free board comprises a tray 11 with upstanding sides 12,and a lid 13 with a tuck in flap 14. The box 10 is shallow and adaptedto contain a frozen pizza. The lid 13 is hinged to the tray 11 along oneedge. A suitable material for the box is for example extruded PET coatedpaper board of an appropriate grade.

[0036] Within the lid 13 is a central circular aperture 15. In the baseof the tray is a circular aluminium foil disc 16. The aperture 15 has adiameter about 40% of the width of the box 10 and the disc has adiameter about 30% of the width of the box 10.

[0037] In use the circular frozen pizza is placed on the tray 11, thelid 13 is closed, and an outer layer of e.g. plastic film is applied tohermetically seal the contents. The outer layer may be for example aclear plastic sleeve, heat sealed along opposite edges and carryingprinted product information. The box may include one or more glued flapsin order to further preserve the integrity thereof during transit.

[0038] After sale, and immediately before heating/cooking, the outerlayer is removed to expose the vent 15, and the box is inserted unopenedinto an oven. The pizza is heated/cooked according to pre-printedinstructions and when ready is removed from the oven for consumption. Asillustrated the box is hinged open, and the sides 12 of the tray 11 maybe collapsed to permit ready serving. These sides 12 may, for example,have lines of weakness at the corners.

[0039] The size, number and pattern of vents may be changed to give arequired heating/cooking characteristic. An alternative enclosure 20 isillustrated in FIG. 2 and has additional radial vents 21, other commonfeatures having the same reference numerals.

[0040] The inside of the trays 10,20 may include a metal or metallisedlayer of foil or other material adapted for direct heating by a sourceof heating energy.

[0041] The tray may further include an oil resistant coating or filmwhereby oil may be added to enhance the heating/cooking process in orderto give a desirable mouth feel and texture to the pizza.

[0042] Although a circular vent and circular metal plate have beendescribed, such shapes are not essential. Other shapes of vent having anattractive or eye-catching appearance are possible whilst ensuring goodproduct appearance after heating. Other shapes of metal plate are alsopossible, and a rectangular or square plate may be preferred to avoidexcessive wastage of material during blanking. The metal plate ispreferably secured to the base of the enclosure by a food compatibleadhesive.

[0043] The vent and plate may be constituted by a plurality of discreteelements such as an array of holes and metal spots adapted to give thedesired appearance to the hot food product.

1. An ovenable container for heating a food product, comprising: upperand lower container portions defining an enclosure for the food product,the upper and lower container portions being formed from a heatresistant material; a vent formed in the upper container portion, thevent defining an open area; and a metal region on the lower containerportion so as to be within the enclosure, the metal region having anarea less than or equal to the open area of the vent.
 2. The ovenablecontainer as claimed in claim 1, wherein the vent is formed in a centralregion of the upper container portion.
 3. The ovenable container asclaimed in claim 1, wherein the upper container portion has an uppersurface area, and the open area of the vent occupies between 5% and 80%of the upper surface area.
 4. The ovenable container as claimed in claim3, wherein the open area of the vent occupies between 20% and 60% of theupper surface area.
 5. The ovenable container as claimed in claim 1,wherein the food product has a shape, and the open area of the vent hasa shape which is substantially the same as the shape of the foodproduct.
 6. The ovenable container as claimed in claim 1, wherein thefood product has a thickness, and the enclosure has a height which isbetween 100% and 150% of the thickness of the food product.
 7. Theovenable container as claimed in claim 1, wherein the lower containerportion has a lower surface area, and the area of the metal regionoccupies between 5% and 80% of the lower surface area.
 8. The ovenablecontainer as claimed in claim 1, wherein the food product is in the formof a circle having a diameter, and the metal region is in the form of acircle having a diameter which is between 25% and 40% of the diameter ofthe food product.
 9. The ovenable container as claimed in claim 1,wherein the open area is in the form of a circle having a diameter, andthe metal region is in the form of a circle having a diameter which isabout 75% of the diameter of the open area.
 10. The ovenable containeras claimed in claim 1, wherein the upper container portion is hingedlyconnected to the lower container portion.
 11. The ovenable container asclaimed in claim 1, wherein the vent has an initial condition in whichthe open area is closed, and a use condition in which the open area isopen.
 12. The ovenable container as claimed in claim 11, furthercomprising a plastic film for closing the open area of the vent in theinitial condition.
 13. The ovenable container as claimed in claim 1,further comprising a layer of an oil resistant material overlying themetal region.
 14. The ovenable container as claimed in claim 1, furthercomprising an embossed support surface on the lower container portionfor supporting the food product.